The Liverpool manager has heard it many times before but this time the chant of "Rafa's cracking up" must have been music to his ears.

It came from the Liverpool supporters, not the Stretford End, its irony marking a first win at Old Trafford under Benítez and another four goals to complete a momentous week. Real Madrid may have been poor at Anfield on Tuesday but these were the champions of Europe, on their own turf, chasing a club record 12th successive league win. Apart from a few minutes in the first half, when Manchester United led through a penalty and their fans briefly had the opportunity to remind Benítez of his alleged resemblance to a fat Spanish waiter, this was a surprisingly one-sided encounter and only one manager looked as though he was enjoying his work.

It was the other one, neatly enough, who sounded as though he might be cracking up. "I thought we were the better team," Sir Alex Ferguson said, making a bid for the wackiest statement of the season. "But the score doesn't reflect that."

The table still does, though United's lead is down to four points and their goal difference cut to five. With a game in hand over Liverpool this may not amount to a turning point, yet results of this magnitude can boost the confidence of winners and eat away at the losers' self-belief. "We are in a better position now, that's all you can say," Benítez said. "If we are going to win the title we are going to need three points from every game and United to drop some more. So it might not happen, but at least we have more confidence."

He can say that again. Confidence oozed through Liverpool from the start, flowing directly from Steven Gerrard and Fernando Torres. The pair were conspicuously head and shoulders above every­one else on the pitch, closely involved in the important goals, and it was tempting to sympathise with Benítez when he bemoaned the fact that this was only the ninth league game of the season they have started together. Perhaps United are not quite as outstanding as everyone has been saying, and Liverpool might be pushing them much closer but for injuries.

With due respect to Ferguson, that was the way it looked here. Nemanja Vidic has been touted as a contender for player of the season but reacted to Torres in the manner of Superman exposed to green kryptonite. The defender was comprehensively beaten for the first Liverpool goal, when he made the mistake of allowing Martin Skrtel's long clearance to bounce and completely underestimated Torres's pace and determination. He almost gave away a penalty on the same player minutes later and completed a miserable afternoon by seeing red for a professional foul on ­Gerrard 15 minutes from time.

Everything looked fairly straightforward for United when they were awarded a penalty after 22 minutes, exactly the sort of thing Benítez might note in his next dossier, though while Park Ji-sung was not exactly carrying the ball goalwards there was no doubt Pepe Reina made ­contact to bring him down. Cristiano Ronaldo stuck away the spot-kick to give United the lead, then promptly returned to ineffective obscurity along with Carlos Tevez and Anderson. Wayne Rooney spent most of the first half gesticulating furiously at his colleagues, though in reality he was not much better. Though always hungry for the ball he rarely used it well and, with the experience of Paul Scholes, Ryan Giggs and Dimitar Berbatov all kept in reserve until the 72nd minute, United found themselves outfought in midfield.

For all that Liverpool's equaliser came out of nothing, Torres taking advantage of momentary United indecision as only he can, significantly he turned provider just before the interval when his measured pass for Gerrard tempted Patrice Evra to take the player instead of the ball and concede a rare home penalty. Gerrard scored it and planted a kiss on a cameraman's lens by way of celebration, clearly not expecting his afternoon to get even better.

All Liverpool needed do was hang on to their lead. The closest United came to scoring in the second half was through a couple of Reina handling mistakes. Yet the home side were so ragged in midfield and nervous in defence they virtually invited their opponents to push for more, and once Vidic had been dismissed for hauling down Gerrard they needed no further asking. Ferguson had just sent on all his three substitutes together but watched powerlessly with them as Fábio Aurélio scored direct from the free-kick. Before Andrea Dossena wrapped things up in the final minute by chipping Edwin van der Sar straight from a Reina clearance, Gerrard missed the easiest chance of the afternoon when he skied into the Stretford End.

It could easily have been five or even six, and if the comprehensiveness of the rout escaped Ferguson, the home fans who left the stadium barely half full by the end seemed to have got the message loud and clear. Those that remained attempted to taunt Liverpool with chants that they would finish the season empty-handed, though that can no longer be taken for granted. While the league remains a big ask, Liverpool will feed off this famous win should the sides' paths cross again in Europe.